ELECTRIC DEPOLARIZATION OF PHOTOSENSITIZED CELLS - LIPID VS PROTEIN ALTERATIONS

We have monitored several photosensitized reactions in proteins, lipos omes and cells under similar conditions. We found that the depolarizat ion of K+-diffusion potential of liposomes or the leakage of an entrap ped molecule, calcein, progress at a much slower rate than the photose nsitized damage to proteins and the photosensitized killing of bacteri al and leukemic cells. X-ray microanalysis revealed that upon light ex posure of HP-treated leukemic cells and bacteria, they totally lost th eir cellular potassium. We deduce that the direct photosensitized oxid ation of lipid components cannot cause the depolarization of cells, wh ich in turn could be responsible for their death. A photosensitized da mage to protein sites in the cell, probably in the membrane, is a more likely reason for the depolarization, the loss of potassium ions and cell death that is caused in light-activated photodynamic processes.